Mobile communication service providers provide voice call and text message services based on second-generation (2G) communication services, and provide transmission of image information based on third-generation (3G) communication services. Furthermore, many researches have been conducted on fourth-generation (4G) communication services to transmit data at a data rate of 100 Mbps or higher. To provide wide-bandwidth and high-speed communication of 4 G communication service, mobile communication service providers conduct many researches on millimeter-wave communication technology.
Communication systems using millimeter waves are used in various application fields. For example, the millimeter-wave communication systems are used for fixed wireless network access systems, transmission between base stations in mobile communication systems, vehicle anti-collision radar systems, and intelligent transport systems (ITS), including outdoor communication systems. Furthermore, the use of the millimeter-wave communication systems may extend to various fields requiring a transmission rate of 100 Mbps or higher.
However, since such millimeter-wave communication systems are fabricated by assembling separate components, the millimeter-wave communication systems are large in size and expensive. Therefore, it is difficult to use the millimeter-wave communication systems for general purposes. For this reason, packaging technology using multiple substrates is actively studied to reduce the size and price of the millimeter-wave communication systems.
Particularly, system in a package (SIP) technology using low temperature co-fired ceramic (LTCC) has developed for various systems such as point-to-multipoint transceivers having an operating bandwidth of about 26 GHz or short-range wireless communication systems having an operating bandwidth of about 60 GHz to 72 GHz.
The millimeter-wave communication systems use various types of millimeter-wave transition apparatuses to reduce transition losses between components. For example, a millimeter-wave transition apparatus in a millimeter-wave communication system for transitioning a millimeter wave between a waveguide and a transmission line.
Hereinafter, a millimeter-wave transition apparatus of the related art will be described with reference to FIGS. 1 and 2. FIG. 1 is a plan view illustrating an apparatus for transitioning a millimeter wave between a standard waveguide and a transmission line according to the related art, and FIG. 2 is a cross-sectional view of the millimeter-wave transition apparatus of FIG. 1.
Referring to FIGS. 1 and 2, the millimeter-wave transition apparatus of the related art includes a standard waveguide 110, a slot 120, and a microstrip 130.
The standard waveguide 110 and the microstrip 130 are connected through the slot 120 so that a signal can transition between the standard waveguide 110 and the microstrip 130. An end of the standard waveguide 110 is stepped or curved for impedance matching.
The standard waveguide 110 has a stepped end as explained above, and the performance of the millimeter-wave transition apparatus is affected by the height and width of the stepped end. However, it is difficult to design and fabricate the stepped end of the standard waveguide 110. That is, in the related art, the shape of the standard waveguide 110 of the millimeter-wave transition apparatus is obtained by varying that of a standard waveguide. As a result, losses increase due to the complicated structure of the standard waveguide 110, and the performance of the millimeter-wave transition apparatus is sensitive to manufacturing errors.
Therefore, what is needed is an efficient millimeter-wave transition structure that can be fabricated without varying the shape of a standard waveguide so as to reduce design and manufacturing times and realize operations less sensitive to manufacturing errors.